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Real-time monitoring of intestinal movement is critical for the clinical diagnosis of bowel diseases, however, the application of organic fluorophores in non-invasive imaging of the intestinal tract via systemic administration is still challenging. We herein report a series of albumin-chaperoned chloro-cyanine dyes for high spatiotemporal tracking of intestinal peristalsis and bowel disease in vivo. By adjusting the size of the central rings, Cy7–5 , with a five-membered ring and meso-chlorine, could covalently bind with circulating endogenous albumin in the blood, generating a bright and stable cyanine-albumin fluorescent complex with ∼1055 nm fluorescence in the near-infrared-II window in situ. Notably, Cy7–5 was able to clearly view intestinal peristalsis by harnessing the inherent intestine tropism of Cy7–5 -albumin complex following intravenous (i.v.) administration. Furthermore, a hydroxyl radical (·OH)-activatable fluorophore (Hydro-Cy7–5) was created, allowing for the selective detection of overproduced ·OH in bowel disease as well as the successful visualization of the inflammatory intestinal tract in vivo after i.v. injection. This work provides a facile strategy for the investigation of intestinal movement and related diseases. [Display omitted] • Five new heptamethine cyanines were synthesized by adjusting the size of the central rings. • Cy7–5 can form a bright and stable covalent complex with albumin in situ to monitor the movement of the intestine. • The overproduced hydroxyl radical (·OH) and inflammatory intestinal tract could be monitored by Hydro-Cy7–5 in vivo. • This work provides a facile strategy to investigate intestinal diseases by harnessing albumin-cyanine complexes. [ABSTRACT FROM AUTHOR]

Since the first use of liposomes as carriers for antigens, much work has been done to elucidate the mechanisms involved in the encapsulation of vaccine-relevant biomolecules. However, only a few studies have specifically investigated the encapsulation of hydrophilic, non-conformational peptide epitopes. We performed comprehensive and systematic screening studies, in order to identify conditions that favor the electrostatic interaction of such peptides with lipid membranes. Moreover, we have explored bi-terminal sequence extension as an approach to modify the isoelectric point of peptides, in order to modulate their membrane binding behavior and eventually shift/expand the working range under which they can be efficiently encapsulated in an electrostatically driven manner. The findings of our membrane interaction studies were then applied to preparing peptide-loaded liposomes. Our results show that the magnitude of membrane binding observed in our exploratory in situ setup translates to corresponding levels of encapsulation efficiency in both of the two most commonly employed methods for the preparation of liposomes, i.e., thin-film hydration and microfluidic mixing. We believe that the methods and findings described in the present studies will be of use to a wide audience and can be applied to address the ongoing relevant issue of the efficient encapsulation of hydrophilic biomolecules.

Abstract: In situ binding of (chimeric) proteins to tissue sections is a widely used method to identify ligands and their localization. Many different protocols for the fixation of frozen tissue sections are used for in situ binding studies. We report the effects of different fixation protocols on the binding pattern observed using in situ binding of an L-selectin–IgM chimeric protein to both rat lymph node and kidney tissue sections. L-selectin is a C-type lectin, expressed on leukocytes and is involved in both lymphocyte homing and migration upon inflammation. We show that different in situ binding patterns in rat kidney are observed using different fixation protocols, including glutaraldehyde, methanol, formaldehyde and acetone fixation. The observed staining is specific, as it can be blocked in the presence of EGTA, an L-selectin blocking antibody or by ligand competition. Enzymatic pre-treatment of the tissue sections using sialidase, heparitinase I or chondroitinase ABC has differential effects on in situ binding depending on tissue type and fixation protocol. These data indicate that special attention should be paid in choosing a fixation protocol for in situ binding studies, especially when using lectins. This could prevent biologically relevant ligands remaining undetected or wrong conclusions being drawn based on the localization of observed binding. [Copyright &y& Elsevier]

Since the first use of liposomes as carriers for antigens, much work has been done to elucidate the mechanisms involved in the encapsulation of vaccine-relevant biomolecules. However, only a few studies have specifically investigated the encapsulation of hydrophilic, non-conformational peptide epitopes. We performed comprehensive and systematic screening studies, in order to identify conditions that favor the electrostatic interaction of such peptides with lipid membranes. Moreover, we have explored bi-terminal sequence extension as an approach to modify the isoelectric point of peptides, in order to modulate their membrane binding behavior and eventually shift/expand the working range under which they can be efficiently encapsulated in an electrostatically driven manner. The findings of our membrane interaction studies were then applied to preparing peptide-loaded liposomes. Our results show that the magnitude of membrane binding observed in our exploratory in situ setup translates to corresponding levels of encapsulation efficiency in both of the two most commonly employed methods for the preparation of liposomes, i.e., thin-film hydration and microfluidic mixing. We believe that the methods and findings described in the present studies will be of use to a wide audience and can be applied to address the ongoing relevant issue of the efficient encapsulation of hydrophilic biomolecules. [ABSTRACT FROM AUTHOR]